Question

The radius of gyration of a body about an axis at a distance of $12cm$ from its centre of mass is $13cm$. Then the radius of gyration of the body about a parallel axis through its C.O.M is (in $cm$):

• A. $25$
• B. $625$
• C. $2.5$
• D. $5$

Answer 1

The correct option is D $5$

$K_1=13cm$
$I_{com}+m(12{)}^2=m(13{)}^2$
$I_{com}=25m.$
Now $K_2$ is radius of gyration about COM.
$m{K}_2^2=25m$
$\Rightarrow K_2=5cm$